Cardiac Pacer And Heart Pulse Monitor

Abstract

A method of and system for remote cardiac diagnosis of cardiac patients, whether or not fitted with implanted cardiac pacer by use of the ordinary telephone. A small transducer transmitter picks up the patient's blood pulses, and cardiac pacer pulses if present, electrically codes them and sends them in proper time sequence through the ordinary telephone transmitter over the telephone lines to a processing center where the coded signals are checked for presence or absence and for the time intervals between adjacent signals of the same coded type and adjacent signals of different coded types. From this data it is possible to determine the operating condition of the cardiac pacer, non-capture and intermittent capture of the heart by the cardiac pacer, cardio-vascular system hemodynamic changes, and cardiac arrhythmias such as missing heartbeat and possible premature ventricular contraction.

Description

This invention relates to a cardiac diagnostic system, and more particularly relates to a diagnostic system for providing follow-up care to persons with implanted cardiac pacers by use of the ordinary telephone without requiring frequent patient visits to the cardiologist.

Cardiac pacers are devices which generate electrical impulses at a recurring rate for the purpose of stimulating the heart muscle to produce normal contractions at a regularly recurring rate in the manner of a normal heart which does not require external electrical stimulation. Cardiac pacers are subject to malfunction by reason of defective parts, battery depletion, and improper conduction of the pacer pacing pulses to the heart muscle due to perhaps a broken electrical lead or a shift of an electrode with respect to the heart muscle itself. In the latter case, it is of course possible for the pacer to itself be functioning in a perfectly proper manner while at the same time being completely ineffective insofar as the performance of its vital function is concerned.

In the past, pacer testing has generally been concerned with attempting to determine whether the pacer is generating its pulse properly, or whether the pulse has deteriorated, usually due to battery depletion. It will be appreciated that a check of pacer pulse performance, while a necessary condition, is not of itself sufficient to insure that the heart of a cardiac patient is in fact being properly paced by the pacer. The system according to the invention provides a simple, inexpensive, convenient and reliable means for quickly determining whether or not the implanted pacer is itself functioning properly and whether or not the cardiac patient is properly responding to the pacer. Specific immediate or incipient problems are immediately detectable, as for example a condition of only intermittent capture of the heart by the pacer a condition of no capture, hemodynamic changes in the circulatory system of the patient, and possible premature ventricular contractions. These physiological conditions are all possible even though the pacer mechanism itself is functioning perfectly, and their early detection can lead to immediate examination by a cardiologist to determine exactly what is happening to the patient so that corrective steps may be taken at a time when they will be effective.

Briefly, the system includes a very small lightweight transducer transmitter device which is in the possession of the patient, and a receiving device which is located at a data processing center which may be in a clinic or at a central processing office. In accordance with a time schedule as determined by the patient's physician, or on an emergency basis, the patient places a telephone call to the processing center, places the telephone headset properly with respect to the transmitter and grasps the transducer transmitter electrodes. The electrical pacer pulse and the subsequent physiological blood pulse of the patient are both picked up by the electrodes, processed in the transmitter and then transmitted out over the telephone line to the data processing receiver center where the information may be processed in a number of different ways to give a complete picture of what is actually happening to the patient.

The results of the processed information are immediately available and the patient can be informed at that time via the telephone connection that every thing is in order or that the patient should be in contact with his or her physician. In the latter event, the physician is of course immediately contacted by the data processing unit and informed of the result of the check just carried out so that the doctor is alerted to the need for taking some action. The data recorded in tangible form at the processing center is immediately transmitted to the physician for his own personal evaluation.

It is a primary object of the invention to provide a novel cardiac diagnostic system by means of which the condition of an implanted cardiac pacer and the physiological responses of the body thereto can be quickly determined by remotely located diagnostic equipment made available to the patient via the ordinary commercial telephone system.

Another object of the invention is to provide a novel cardiac diagnostic system as aforesaid which utilizes a small lightweight transducer device retained by the cardiac patient and by means of which the requisite diagnostic information is obtained from the patient and transmitted into the telephone system.

A further object of the invention is to provide a novel cardiac diagnostic system as aforesaid wherein the transducer apparatus processes the electrical pacer pulses and the physiological patient blood pulses to provide time related electrical signals from which a diagnosis of the functioning condition of the pacer and the physiological cardiac condition of the patient are quickly determinable.

The foregoing and other objects of the invention will become clear from reading the following specification in conjunction with an examination of the appended drawings, wherein:

FIG. 1 is a pictorial diagrammatic representation of the transmitting portion of the system and a representative part of the receiving portion of the system according to the invention;

FIG. 2 is a functional block diagram of the apparatus utilized in the diagnostic system for effecting a complete cardiac diagnosis according to the invention; and

FIG. 3A to 3I is a nine part timing diagram illustrating the general form of information derived from the cardiac patient and the subsequent processing thereof together with illustrations of various types of conditions which can occur and which are detectable for diagnosis.

In the several figures, like elements are denoted by like reference characters.

Referring now to the drawings, and first to FIG. 1 and 2, there is seen the transducer transmitter designated generally as 10 and the data receiver and processor designated generally as 11 which are intercoupled by the commercial telephone system designated generally at 12 and terminating at the transmitting and receiving ends respectively with the hand sets 13 and 14.

The transducer transmitter 10 is held in a suitable flat hinged case 15 having a battery power supply 16 which energizes the circuitry of the device through switch 17 when the case 15 is opened, and which disconnects the power supply from the circuitry when the case is closed. The electronic processing apparatus contained within the region 18 of the case 15 includes amplifiers 19 and 20 which are respectively fed signals from pacer pulse pick-up electrode 21 and blood pulse pick-up electrode 22 through signal cables 23 and 24. Amplifier 19 amplifies the electrical pacer pulse to insure the triggering of a monostable trigger circuit 25 which generates a square pulse 26 which is then differentiated and clipped by differentiater clipper 27 to provide a sharp pulse 28 from the leading edge of square pulse 26 while suppressing the sharp pulse generated by the trailing edge of square pulse 26. The blood pulse amplified by amplifier 20 is used to trigger a triggered oscillator 29 to provide a timed burst of audio frequency oscillation 30 which might typically be on the order of two thousand to twenty-five hundred Hertz. The derived pacer pulse 28 and audio burst 30 are, as will be subsequently seen, routed to speaker driver 31 in temporally spaced sequence and are then converted to audio signals by the loud speaker 32 which transmits them through a sound tunnel 33 to the transmitter 34 of telephone hand set 13.

Since the heart muscle contracts in response to the electrical pacer pulse, the order of events is such that the electrical pacer pulse is generated first and is then followed by the blood pulse resulting from contraction of the heart muscle. The blood pulse can be picked up at any convenient point on the body such as the nose, forehead or a finger or toe, and the time interval between contraction of the heart muscle and pick-up of the blood pulse is determined by the distance between the heart and the point at which the blood pulse is picked up. As illustrated, the finger is a convenient point for pick-up and a suitable finger pulse pick-up device typically could be that manufactured by the Sanei Instrument Company of Japan which is sensitive to shifts in the red spectrum and produces a voltage change with variations in blood flow. The timing intervals to be hereafter mentioned in connection with the timing diagram of FIG. 3 are all intervals which would occur for blood pulses which are detected at the fingers of the patient.

The train of signals 28 and 30 after injection into the transmitter 34 of telephone hand-set 13 proceed through the telephone system 12 to the receiver 35 of the telephone hand-set 14 at the data processing center where they are amplified by telephone amplifier 36 and transmitted via cable 37 to one or more pieces of terminal equipment, such as to loudspeaker 38 via cable 39 for the generation of audible signals in the form of a tick representing the pacer pulse followed by a tone representing the blood pulse.

The terminal equipment of more significance however would be the strip recorder 40 of the moving stylus type and the interval counter 41 which typically could be a Monsanto 100B counter. The interval counter is a device which provides a read-out of the time interval between selected events. For example, a digital read-out can be obtained for the time interval between successive derived pacer pulse spikes 28 in order to determine the pacer pulse rate and whether or not the rate is constant within the allowed tolerance limits. The counter can also be selectively set to determine the same information for pulses derived from the burst 30 of audio frequency signal which corresponded to the occurrence of the physiological blood pulse of the patient. Additionally, and of great importance, is the measurement of time interval between the occurrence of a derived pacer pulse 28 and a pulse corresponding to the occurrence of the physiological blood pulse. Since the information on cable 37 is in fact the pacer pulse 28 and the audio tone 30, two things must be done in order to properly present the data to the interval counter 41.

First, the derived pacer pulse 28 must be separated from the audio burst 30 with the former being permitted to pass to the interval counter 41 while the latter is suppressed. This is carried out by the high pass filter 42 which passes the derived relatively high frequency pacer pulse 28 while supressing the relatively lower frequency tone burst 30 so that the input to interval counter 41 on line 43 consists only of the succession of derived pacer pulses 28.

Secondly, the audio tone burst 30 must be separated from the derived pacer pulse 28 and converted into a pulse input of suitable waveform for use as a signal input to the interval counter 41. This is accomplished by the demodulator 44 which envelope detects the low frequency tone burst 30 while suppressing the relatively high frequency derived pacer pulse 28, and the differentiator clipper 45 which produces a derived blood pulse 46 from the leading edge of the demodulated audio burst signal while clipping the trailing edge pulse. The derived blood pulse 46 is injected at the interval counter 41 via the signal input line 47.

The interval counter 41 is provided with an output signal connection which provides an output signal that changes from a logical "one" to a logical "zero" when the count is started and reverses when the count is terminated, thus providing a step function output which may be applied to integrator 57. Should the count exceed a predetermined set value, the integrated output signal level reaches a magnitude sufficient to trigger the Schmitt trigger 58 and actuate an alarm 59 of whatever type is desired.

The elements shown in the functional block diagram of FIG. 2 are all well known and need not be described in detail, and any functionally equivalent particular form of element would be equally suitable. For example, the demodulator 44 need not be an envelope detector, but could for example be a high Q filter tuned to the audio burst frequency 30 and followed by a suitable form of trigger circuit and differentiator to produce the desired derived blood pulse 46. The particular form of demodulator 44 is not significant, it is the signal separating the waveshaping function which is of importance.

Turning now to a consideration of the timing diagrams of FIG. 3, it is observed that nine timing times A through I are illustrated, depicting various diagnostic conditions to be now described.

The diagram 3A shows a repetitive sequence of pulse waveforms beginning with a relatively high amplitude wave having a steep leading edge, and followed by two waveforms of low amplitude with the pattern being thereafter successively repeated. The high amplitude wave designated as 48 corresponds to the R-wave of the EKG tracing of a typically paced heart, while the succeeding low amplitude waves 49 and 50 represent respectively the T-wave and the P-wave. The steeply rising leading edge of the R-wave occurs immediately after the time of the pacer pulse spikes designated as 28 in FIGS. 3C and 3E through 3I although the time scale is such that the separation is not visible. These pacer pulse spikes are observed to occur at the times designated as t.sub.o, t.sub.2 and t.sub.4. FIG. 3B illustrates the general form of the blood pulse waveform picked up at the finger by the finger pulse pick-up 22, and these are also observed to be cyclically repetitive and occur at times t.sub.1 and t.sub.3. In a normal situation, the time interval (t.sub.1 - t.sub.o) will be equal to (t.sub.3 - t.sub.2) and will be approximately 0.6 seconds .+-. 0.15 seconds.

FIG. 3C illustrates the derived pacer pulses 28 as previously described with the intervals (t.sub.2 - t.sub.o) = (t.sub.4 - t.sub.2) = .DELTA.t .+-. 0.3 milliseconds where the time interval .DELTA.t is chosen by the physician with respect to the particular patient and will lie normally within the range of 500 to 1,200 milliseconds. FIG. 3D illustrates the tone bursts 30 derived from the blood pulse waveforms 51 illustrated in FIG. 3B, these bursts 30 occuring at time intervals (t.sub.3 - t.sub.1) which should be equal to the previously defined .DELTA.t .+-. approximately 30 milliseconds.

The showing of FIG. 3E is a combination of the waveforms of FIG. 3C and FIG. 3D showing the normal pattern of occurrance of a pacer pulse followed at the appropriate time by a blood pulse with the two signals repeating cyclically over and over as shown. Such a pulse pattern of course illustrates a properly functioning cardiac pacer putting out its pulses at the proper time and resulting in complete capture of the heart muscle with the consequent regular rhythmic contractions of the heart producing the desired blood pulse pattern.

The timing patterns of FIG. 3F through FIG. 3I illustrate abnormal conditions which are detectable by the cardiac diagnostic system according to the invention. These abnormal conditions are usually detectable at a sufficiently early point in time so that remedial action can be taken before the development of any critical condition occurs. FIG. 3F illustrates a regularly occurring series of pacer pulses 28 in which the first and third pulses are followed by pulses 46 corresponding to the occurrence of blood pulses. However, it is observed that there are no blood pulses 46 following the second and fourth pacer pulses 28, indicating that the second and fourth pacer pulses 28 were ineffective in causing a contraction of the heart muscle. This type of pulse pattern indicates only intermittent capture of the heart by the cardiac pacer, and also indicates the patient should immediately consult his cardiologist because such a pattern indicates either physiological changes requiring attention or some problem associated with proper transfer of the pacer pulse to the heart muscle. The regularity of the pacer pulses 28 of course rules out any malfunction of the electrical circuitry of the cardiac pacer itself.

FIG. 3G discloses a pattern of regularly occurring equally spaced pacer pulses 28 together with a series of three blood pulse signals 52a, 52b and 52c which respectively follow the first, second and fourth pacer pulses. It will be observed that the spacing of the pulses 52a, 52b and 52c with respect to their immediately preceding pacer pulses 28 is of a random time nature, and that there is no blood pulse signal whatever following the third pacer pulse 28. The missing blood pulse and random blood pulse intervals indicate a condition of no capture of the heart muscle by the cardiac pacer. This is a serious condition and must be remedied at the earliest possible time.

FIG. 3H again illustrates a regularly occurring sequence of pacer pulses 28 followed however by a regularly occurring series of blood pulses 53, one such pulse 53 occurring after each pacer pulse 28. However, comparison of the timing diagram of FIG. 3H with that of FIG. 3E discloses that the blood pulses 53 are occurring at a much earlier time after the occurrence of a pacer pulse, and in fact as shown in FIG. 3H with an interval of (t.sub.1 - t.sub.o) of approximately 0.5 seconds. The regularity of occurrence of the blood pulses 53 with respect to the pacer pulses 28 indicates that complete capture of the heart muscle by the pacer exists, but that some hemodynamic change has occurred within the physiological system of the cardiac patient which has shortened the time interval within which the heart muscle responds to the cardiac pacer pulse. In this case, the patient will also be referred to his physician so that a determination can be made as to the significance of the changed conditions with respect to the particular patient involved. Such a change may or may not be the forerunner of a serious condition and can only be determined by a thorough medical diagnosis.

FIG. 3I illustrates a normally functioning cardiac pacer properly generating a sequence of pacer pulses 28 in which the seocnd, third and fourth pacer pulses 28 are followed by regularly occurring blood pulses 54 temporally spaced from the preceding pacer pulse by equal amounts. However, it is observed that the first pacer pulse 28 is followed by a pair of blood pulses 55 and 56 instead of by only a single blood pulse, and that both of the blood pulses 55 and 56 are temporally spaced from the preceding pacer pulse 28 by time intervals which are different from the time interval of blood pulses 54 which follow the subsequent pacer pulses 28. The first blood pulse 55 is one which occurs independently of the pacer pulse 28 while the second blood pulse 56 is caused by the pacer pulse 28 but is delayed in time due to the occurrence of the immediately preceding blood pulse 55. This condition could indicate possible premature ventricular contraction which could be the first indicator of the incipient onset of ventricular fibrillation, and again represents a condition requiring the attention of the attending physician.

From the foregoing discussion of the timing diagrams of FIG. 3, it will be appreciated that merely checking the implanted cardiac pacer itself to determine whether or not it is generating pacer signals, while necessary, is totally inadequate as a determinant of the condition of the patient's cardiac system since all of the problem conditions just described in connection with the showings of FIGS. 3F through 3I in fact occur under circumstances where the electrical cardiac pacer is to all intents and purposes properly generating its pacing pulses. Accordingly, it should now be understood that the cardiac diagnostic system according to the invention enables rapid and early diagnosis of incipient cardiac problems before they actually become troublesome so that remedial measures can be immediately undertaken to anticipate and avoid the occurrence of serious or even fatal cardiac conditions.

Patients without cardiac pacer can use just the blood pulse detecting features, to transmit information to the data center which can be used to determine the presence of cardiac arrhythmias. This can be especially significant for the post coronary patient. Moreover, detection of the existence of a patient's "R" wave can also be provided by using an R-wave sensing circuit in the amplifier 19 in conjunction with the blood pulse detection to provide data, via the telephone, as to the sequence of mechanical and electrical events of the cardiac system for patients without pacemakers.

Specifically, the complete EKG will not be transmitted, only the timing of the R wave to R wave interval is necessary, so only a pulse corresponding to the R wave need be transmitted, as is done with the pacer spike.

Having now described the invention in connection with a particularly illustrated embodiment thereof, it will be appreciated that variations and modifications of the invention may now occur from time to time to those persons normally skilled in the art without departing from the essential scope or spirit of the invention, and accordingly it is intended to claim the same broadly as well as specifically as indicated by the appended claims.

Claims

I claim:

1. A method of cardiac diagnosis for detection of abnormal cardiac conditions in patients remote in distance from the diagnostic center, consisting of the steps of,

a. detecting the occurrence of each of a continuous sequence of the patient's physiological blood pulses,

b. converting such blood pulses as they occur to a sequence of non-analog timing signals for transmission through a commercial telephone system and thereby generating a sequence of electrical signals occurring in the same timed relationship to one another as the timed relationship between the blood pulses to which they correspond,

c. inserting the sequence of electrical signals into a commercial telephone system and transmitting the signals to a data processing center where the following steps are carried out,

d. detecting the timed sequence of electrical signals,

e. measuring, displaying and recording in units of time the time interval between each successive pair of signals of the sequence,

f. comparing the aforesaid measured time intervals against one another, and

g. indicating the displayed time intervals and whether or not the compared time intervals differ from one another by more than a predetermined length of time,

whereby, conditions of cardiac arrhythmias, such as missing heartbeat and possible premature ventricular contraction are detectable.

2. A method of cardiac diagnosis as described in claim 1 wherein the step of comparing the measured time intervals against one another further includes comparing the aforesaid time intervals against standard time intervals previously established by the physician as normal for the particular person being monitored.

3. A method of cardiac diagnosis as described in claim 1 wherein the step of converting each blood pulse consists of the steps of, first converting the blood pulse to an electrical analog signal and then converting the analog signal to a non-analog electrical signal designating only the time of occurrence of the blood pulse.

4. A method of cardiac diagnosis as described in claim 1 wherein the steps of converting each blood pulses consists of the steps of, first converting the blood pulse to an electrical analog signal, then converting the analog signal to a non-analog tone burst electrical signal, then converting the non-analog electrical tone burst signal to an acoustical signal within the bandpass of the transmitter of a commercial telephone.

5. A method of cardiac diagnosis for detection of abnormal conditions in cardiac pacer patients remote in distance from the diagnostic center, consisting of the steps of,

a. detecting the occurrence of each of a continuous sequence of cardiac pacer pulses, and detecting the occurrence of each of a continuous sequence of the patient's physiological blood pulses,

b. converting each such pacer pulse and blood pulse as it occurs to a signal for transmission through a commercial telephone system and thereby generating a sequence of electrical signals occurring in the same timed relationship to one another as the timed relationship between the pacer pulses and blood pulses to which they correspond,

c. inserting the sequence of electrical signals into a commercial telephone system and transmitting the signals to a data processing center where the following steps are carried out,

d. detecting the timed sequence of electrical signals,

e. measuring the time intervals between selected pairs of signals of the sequence,

f. comparing the aforesaid measured time intervals against one another, and

g. indicating whether or not the compared time intervals differ from one another by more than a predetermined length of time,

whereby, conditions of cardiac pacer failure, non-capture and intermittent capture of the heart by the pacer, cardio-vascular system hemodynamic changes, cardiac arrhythmias, such as missing heartbeat, and possible premature ventricular contraction are detectable.

6. A method of cardiac diagnosis as described in claim 5 wherein the step of comparing the measured time intervals against one another further includes comparing the aforesaid time intervals against standard time intervals previously established by the physician as normal for the particular person being monitored.

7. A method of cardiac diagnosis as described in claim 5 wherein detecting the occurrence of the pacer pulses and detecting the occurrence of the blood pulses are carried out independently of one another, and wherein converting the pacer pulses and blood pulses to a sequence of timed electrical signals includes the step of combining the pulses into a single sequence of pulses.

8. A method of cardiac diagnosis as described in claim 5 wherein the step of measuring the time intervals between selected pairs of signals of the sequence includes the step of first separating the sequence of timed electrical signals into a first sequence of signals corresponding only to pacer pulse signals and a second sequence of signals corresponding only to blood pulse signals.

9. A method of cardiac diagnosis as described in claim 8 wherein the step of separating the sequence of timed electrical signals into the aforesaid first and second sequences and selectively following the signals separating step by one or more of the following steps,

a. the step of measuring the time interval between each successive pair of signals of said first sequence,

b. the step of measuring the time interval between each successive pair of signals of said second sequence,

c. the step of measuring the time interval between each successive pair of signals in which the first signal of the pair is selected from said first sequence and the second signal of the pair is selected as the next occurring signal from said second sequence.

10. A method of cardiac diagnosis as described in claim 5 wherein the step of measuring the time intervals between selected pairs of signals of the sequence includes the step of first separating the sequence of electrical signals, and selecting either or both of a first sequence of signals corresponding only to pacer pulse signals and a second sequence of signals corresponding only to blood pulse signals.

11. A cardiac diagnostic system for detection of abnormal cardiac conditions in patients located remotely from a diagnostic center, comprising in combination,

a. a transducer transmitter comprising,

1. first detection means for detecting the occurrence of each of a continuous sequence of the patient's physiological blood pulses,

2. converter means operatively coupled to said first detection means effective to convert such blood pulses as they occur to a sequence of non-analog timing signals for transmission through a commercial telephone system, and thereby being capable of generating a sequence of electrical signals occurring in the same timed relationship to one another as the timed relationship between the blood pulses to which they correspond.

3. means adapted to be coupled to a commercial telephone system effective to insert the said sequence of signals into a commercial telephone system to transmit the signals to a data processing center,

b. a receiver processer at the data processing center comprising,

1. second detection means adapted to be coupled to a commercial telephone system effective to detect the timed sequence of signals inserted at the transmitting point,

2. signal presentation means coupled to said second detection means for measuring, displaying and recording in units of time the time intervals between successive pairs of signals of the sequence,

whereby, conditions of cardiac arrhythmias, such as missing heartbeat, and possible premature ventricular contraction are detectable.

12. A cardiac diagnostic system as described in claim 11 wherein said first detection means comprises a transducer which generates a discrete analog electrical signal upon detection of each blood pulse, and wherein said converter means converts each of said discrete analog electrical signal to a standardized non-analog waveform.

13. A cardiac diagnostic system as described in claim 11 wherein said receiver processer signal presentation means comprises measuring means effective to automatically measure the time intervals between successive pairs of the sequence and provide a read-out of the measurement in units of time.

14. A cardiac diagnostic systems as described in claim 13 wherein said measuring means read-out includes an electrical signal read-out representing the time interval just measured, said receiver processer further including a comparator device coupled to said measuring means and effective responsive to said electrical signal read-out from the latter to actuate an alarm when the time interval represented thereby differs by more than a predetermined amount from a standard time interval selectively programmed into said comparator device.

15. A cardiac diagnostic system for detection of abnormal cardiac conditions in patients located remotely from a diagnostic center, comprising in combination,

a. a transducer transmitter comprising,

1. first detection means for detecting the occurrence of each of a continuous sequence of cardiac pacer pulses, and detecting the occurrence of each of a continuous sequence of the patient's physiological blood pulses,

2. converter means operatively coupled to said first detection means effective to convert each such pacer pulse and each such blood pulse as it occurs to a signal for transmission through a commercial telephone system, and thereby generating a sequence of electrical signals occurring in the same timed relationship to one another as the timed relationship between the pacer pulses and the blood pulses to which they correspond,

3. means adapted to be coupled to a commercial telephone system effective to insert the said sequence of signals into a commercial telephone system to transmit the signals to a data processing center,

b. a receiver processer at the data processing center comprising,

1. second detection means, adapted to be coupled to a commercial telephone system effective to detect the timed sequence of signals inserted at the transmitting point,

2. signal presentation means coupled to said second detection means for measuring, displaying and recording in units of time the time intervals between selected pairs of signals of the sequence,

whereby, conditions of cardiac pacer failure, non-capture and intermittent capture of the heart by the cardiac pacer, cardio-vascular system hemodynamic changes, cardiac arrhythmias such as missing heartbeat, and possible premature ventricular contraction are detectable.

16. A cardiac diagnostic system as described in claim 15 wherein said receiver processer signal presentation means comprises measuring means effective to automatically measure the time intervals between selected pairs of signals of the sequence and provide a read-out of the measurement in units of time.

17. A cardiac diagnostic system as described in claim 15 wherein said first detection means comprises transducer means which generates a first discrete electrical signal upon detection of each pacer pulse and which generates a second discrete electrical signal upon detection of each blood pulse, and wherein said converter means converts said first and second discrete electrical signals respectively into first and second signals of different frequency and combines said signals of different frequency into a single sequence.

18. A cardiac diagnostic system as described in claim 16 wherein said measuring means comprises sorting means effective to separate the timed sequence of signals into a first sequence of signals corresponding only to pacer pulse signals and a second sequence of signals corresponding only to blood pulse signals.

19. A cardiac diagnostic system as described in claim 16 wherein said measuring means read-out includes an electrical signal read-out representing the time interval just measured, and said receiver processer further includes a comparator device coupled to said measuring means and effective responsive to said electrical signal read-out from the latter to actuate an alarm when the time interval represented thereby differs by more than a predetermined amount from a standard time interval selectively programmed into said comparator device.

20. A cardiac diagnostic system as described in claim 17 wherein said receiver processer signal presentation means comprises measuring means effective to automatically measure the time intervals between selected pairs of signals of the said single sequence of signals and provide a read-out of the measurement.

21. A cardiac diagnostic system as described in claim 20 wherein said measuring means comprises sorting means effective to separate said signals of different frequency in said single sequence of signals into a first sequence of signals corresponding only to pacer pulse signals and a second sequence of signals corresponding only to blood pulse signals.

22. A cardiac diagnostic system as described in claim 21 wherein said measuring means includes selection means for measuring the time intervals between one or more of the following:

a. each successive pair of signals of said first sequence,

b. each successive pair of signals of said second sequence,

c. each successive pair of signals in which the first signal of the pair is selected from said first sequence and the second signal of the pair is selected as the next occurring signal from said second sequence.